Hybrid powertrains for vehicles utilize different power sources under different vehicle operating conditions. An electro-mechanical hybrid powertrain typically has an internal combustion engine, such as a diesel engine, gasoline engine, air engine, or fuel cell, and one or more motor/generators. Different operating modes, such as an engine-only operating mode, an electric-only operating mode, and an electrically-variable operating mode are established by engaging brakes and/or clutches in different combinations and controlling the engine and motor/generators. The various operating modes are advantageous as they may be used to improve fuel economy. However, the additional components required for a hybrid powertrain, such as the motor/generators, planetary gear sets, brakes and/or clutches may increase overall vehicle cost.